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Hin RC, Coath CD, Carter PJ, Nimmo F, Lai YJ, Pogge von Strandmann PAE, Willbold M, Leinhardt ZM, Walter MJ, Elliott T. Magnesium isotope evidence that accretional vapour loss shapes planetary compositions. Nature 2017; 549:511-515. [PMID: 28959965 PMCID: PMC5624506 DOI: 10.1038/nature23899] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 08/04/2017] [Indexed: 11/13/2022]
Abstract
It has long been recognized that Earth and other differentiated planetary bodies are chemically fractionated compared to primitive, chondritic meteorites and, by inference, the primordial disk from which they formed. However, it is not known whether the notable volatile depletions of planetary bodies are a consequence of accretion or inherited from prior nebular fractionation. The isotopic compositions of the main constituents of planetary bodies can contribute to this debate. Here we develop an analytical approach that corrects a major cause of measurement inaccuracy inherent in conventional methods, and show that all differentiated bodies have isotopically heavier magnesium compositions than chondritic meteorites. We argue that possible magnesium isotope fractionation during condensation of the solar nebula, core formation and silicate differentiation cannot explain these observations. However, isotopic fractionation between liquid and vapour, followed by vapour escape during accretionary growth of planetesimals, generates appropriate residual compositions. Our modelling implies that the isotopic compositions of magnesium, silicon and iron, and the relative abundances of the major elements of Earth and other planetary bodies, are a natural consequence of substantial (about 40 per cent by mass) vapour loss from growing planetesimals by this mechanism.
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Affiliation(s)
- Remco C Hin
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
| | - Christopher D Coath
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
| | - Philip J Carter
- School of Physics, University of Bristol, H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, UK
| | - Francis Nimmo
- Department of Earth and Planetary Sciences, University of California, Santa Cruz, Santa Cruz, California 95064, USA
| | - Yi-Jen Lai
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
| | - Philip A E Pogge von Strandmann
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
- London Geochemistry and Isotope Centre, Department of Earth Sciences, University College London, and Department of Earth and Planetary Sciences, Birkbeck, University of London, Gower Street, London WC1E 6BT, UK
| | - Matthias Willbold
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
| | - Zoë M Leinhardt
- School of Physics, University of Bristol, H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, UK
| | - Michael J Walter
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
| | - Tim Elliott
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
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Marrocchi Y, Chaussidon M, Piani L, Libourel G. Early scattering of the solar protoplanetary disk recorded in meteoritic chondrules. SCIENCE ADVANCES 2016; 2:e1601001. [PMID: 27419237 PMCID: PMC4942334 DOI: 10.1126/sciadv.1601001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 06/10/2016] [Indexed: 06/02/2023]
Abstract
Meteoritic chondrules are submillimeter spherules representing the major constituent of nondifferentiated planetesimals formed in the solar protoplanetary disk. The link between the dynamics of the disk and the origin of chondrules remains enigmatic. Collisions between planetesimals formed at different heliocentric distances were frequent early in the evolution of the disk. We show that the presence, in some chondrules, of previously unrecognized magnetites of magmatic origin implies the formation of these chondrules under impact-generated oxidizing conditions. The three oxygen isotopes systematic of magmatic magnetites and silicates can only be explained by invoking an impact between silicate-rich and ice-rich planetesimals. This suggests that these peculiar chondrules are by-products of the early mixing in the disk of populations of planetesimals from the inner and outer solar system.
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Affiliation(s)
- Yves Marrocchi
- Centre de Recherches Pétrographiques et Géochimiques, CNRS, Université de Lorraine, UMR 7358, 54501 Vandoeuvre-lès-Nancy, France
| | - Marc Chaussidon
- Institut de Physique du Globe de Paris, Université Sorbonne Paris Cité, 75238 Paris, France
| | - Laurette Piani
- Department of Natural History Sciences, Hokkaido University, Sapporo 060-0810, Japan
| | - Guy Libourel
- Observatoire de la Côte d’Azur, CS 34229, 06304 Nice, France
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